LED lighting has gradually gained traction in a market once dominated by traditional lighting products such as incandescent light bulbs due to several advantages, including lower energy consumption and higher brightness. The development of LED lighting technology still has challenges, including energy consumption and heat dissipation.
Many LED lights are disclosed in the prior art. For example, Chinese Patent Publication No. 101749675A and United Kingdom Patent Publication No. 2467027 disclose an LED light assembly which includes a plurality of LED PCBs, with each PCB having at least one LED bulb and electrical connector pads configured at each opposite end of the boards. At least one electrical connector is configured to connect one end of a first PCB to an end of a second PCB such that the first and second PCBs are electrically connected to each other. This type of assembly is placed in structures which connect to lighting fixtures designed for conventional fluorescent lighting. The publications disclose that a plurality of LEDs can be mounted on a PCB, and multiple PCBs can be joined by connectors to form an LED light. This is a change from traditional lighting assemblies. Mass production of this kind of LED light is difficult due to its costly manufacturing processes and assembly.
Chinese Patent Publication No. 102506338A discloses an LED strip which comprises a PCB and a plurality of LEDs mounted on the PCB; a heat sink mounted on the back of the PCB; and a heat conductive adhesive disposed between the PCB and the heat sink fin. Fins protrude from the heat sink. The publication discloses how to mount an LED on a PCB with a heat sink and radiating fins to form a striped LED lamp. The heat dissipation characteristics were not disclosed and so the efficiency of the system is unknown.
Underutilizing the maximum rated drive current of an LED is referred to as underdriving the current. For example, an LED which has a normal power consumption of 1 watt (W) may yield 120 lumens. If less current is driven through the same circuit, the power used by the LED as well as the lumen output will be reduced. As current is decreased, power will decrease faster than lumen output. For example, the same LED operated at half power or 0.5 W may produce 70 lumens. Therefore, this known technique, yields a better electricity to light output conversion efficiency. More LEDs need to be added to the circuit in order to achieve the desired lumen output. Underdriving the LEDs does not use LEDs to their maximum lumen potential. As such, while less power will be required to achieve the same lumen output, the light will employ more LEDs, which is more expensive. Because of the higher operating efficiency of the individual LEDs, the total amount of heat dissipated is reduced.
Overutilizing the maximum rated drive current of an LED is referred to as overdriving the current. Most prior art LED lighting overdrives the LEDs which requires less LEDs per light and increases heat dissipation challenges, which are resolved with fans and complex heat fin systems. Significantly, overdriving LEDs reduces the luminous efficacy or efficiency of the light, measured as lumens per watt (lm/W), since a higher current is driven through an LED which is rated for a relatively lower normal rating. Furthermore, overdriving the LEDs will reduce their useful operating life, sometimes significantly if heat dissipation is not accordingly enhanced.
Generally most indoor and task lighting has a Correlated Color Temperature (CCT) in the range of 2,700-4,000 K and a Color Rendering Index (CRI) of at least 70 or higher. A traditional incandescent 100 W A19 light bulb in this color temperature range produces about 1,600 lumens of light, with an efficiency of 16 lm/W. Compact fluorescent lights (CFL) which produce the same amount of light yield at about 66 lm/W. Equivalent prior art LED lights yield about 70 to 80 lm/W.
Governments are incentivizing the development of more efficient lighting solutions. In 2011, the United States Department of Energy awarded the L Prize™ for a very efficient 60 W replacement LED light to Philips Lighting North America. The Philips award-winning LED light consumes 9.7 W and has a light output of 910 lumens and color temperature of 2,727 K, yielding an efficiency of about 94 lm/W. That light bulb has been discontinued from the market and replaced with lower efficiency variants. By the end of 2014, the Government of Canada will have banned sales of most standard incandescent light bulbs in favour of more efficient lighting.
Manufacturers have experienced much difficulty in improving the efficiency of 100 W replacement LED bulbs, in part due to the heat dissipation problems. In 2011, Osram Sylvania announced a laboratory result for a 100 W replacement LED light achieving 1,500 lumens with 14 W, yielding 107 lm/W in the color temperature range of 2,700 K.
There is a need for a more efficient light with acceptable CCT and CRI and having at least a 1,600 lumen output. There is also a need to improve LED lighting to provide more efficient lighting and better heat dissipation characteristics to minimize energy consumption.